By inputting a starting point and destination point, a navigation device or route planner determines a “reasonable route” between the input starting point and destination point. Normally, the route with the shortest travelling time or the shortest travelling distance is meant by “reasonable route”.
The calculated route is determined as a graph from nodes and edges, wherein in general road intersections or junctions correspond to the nodes and road segments between adjacent road intersections or junctions correspond to the edges. Hereby, road segments may be characterised by additional parameters, such as the length, road type, speed limit, etc. With the aid of these parameters, weights are calculated for the road segments and the route is then calculated on the basis of these weights. Such weights may, however, also be already firmly allocated to the road segments in the cartographic data.
When planning a route, there is often a need to manipulate a precalculated route subsequently. For example, places in the vicinity of the precalculated route may be of interest to a user for making an intermediate stop. However, it is also conceivable that a user prefers less busy roads along the route to those roads (e.g. motorways) preset by the navigation device or route planner. In this case, the planning may become tedious since individual intermediate destination points have to be input.
A simplification of the route planning is achieved (cf. Google maps) by making the route displayed on the screen graphically editable with the aid of a cursor. In this case, with the aid of the cursor an appropriate point on the precalculated route is marked and dragged to another position on the map. The route is then appropriately adapted to the new position of the point. A disadvantage of this method is that the cursor has to be made to coincide with the displayed route on the screen in order to be able to carry out a modification.